1. Field of the Invention
The present invention relates to a method of manufacturing an electrical-resistance heating element, such as a heater, an electrostatic chuck, or an RF susceptor, to be applied to a semiconductor manufacturing apparatus such as a thermal CVD apparatus or an etching apparatus.
2. Description of the Related Art
In the field of semiconductor manufacturing technology, a wafer or the like is often subjected to processes such as plasma etching, chemical vapor deposition (CVD), and ion plating. For these processes, a heating apparatus (or a heater) is used as a component for heating the wafer, and an electrostatic chuck and an RF susceptor is used as a component for fixing or holding the wafer.
The semiconductor manufacturing apparatus such as the CVD apparatus or the etching apparatus, mentioned above, typically uses corrosive gas, such as chlorine gas or fluorine gas, for deposition, etching, or cleaning. Heretofore, a resistance-heating element having a surface coated with a metallic material such as stainless steel has been used as the heater. However, conventional semiconductor manufacturing apparatuses have a problem of particles developing. More specifically, the heater or the susceptor is corroded by corrosive gas such as chlorine gas, and thus, chloride, oxide or other particles develop on the inside surface of the heater or the susceptor.
Japanese Patent Application Laid-Open Publication No. 6-151332 discloses, in FIG. 1 and its corresponding description on page 2, an approach for preventing particles from developing. The application discloses a ceramic heating resistor including a susceptor made of a dense ceramic material having corrosion resistance, a resistance-heating element made of a high melting point metal, and a plasma-generating electrode, wherein the resistance-heating element and the plasma-generating electrode are embedded in the susceptor.
First, a method of manufacturing the ceramic heating resistor mentioned above includes forming a preform by charging ceramic powder into a press tool; and forming a continuous concave or groove in the surface of the preform along a predetermined planar pattern. Then, the method includes forming a resistance-heating element by bonding terminals on both ends of a winding of a high melting point metal wire; placing the resistance-heating element in the concave or groove; charging ceramic powder on the resistance-heating element; and performing molding. The method further includes disposing a meshed RF electrode on a molded form having the resistance-heating element embedded therein; charging ceramic powder on the electrode; and then performing molding. Then, the method includes uniaxially pressing the ceramic powder into a disc-shaped molded form; and sintering the disc-shaped molded form by means of hot pressing.
In the ceramic heating resistor manufactured by the method mentioned above, the resistance-heating element made of the high melting point metal is embedded in the dense ceramic base material. Thus, the ceramic heating resistor can directly heat a wafer as placed thereon, so that the ceramic heating resistor can achieve improvements in soaking characteristics and heating response. Moreover, the plasma-generating electrode is embedded in the ceramic base material, thus having the properties of insulation from a surface on which a wafer is placed. Thus, the ceramic heating resistor can eliminate direct application of a current to a wafer placed thereon, so that a wafer can be placed directly on the ceramic heating resistor without the risk of contamination. Therefore, the ceramic heating resistor has the advantage of enabling efficient heating of a wafer.
However, the method of manufacturing the ceramic heating resistor mentioned above has the problem of shrinkage of the molded form incident to densification which occurs during sintering, because the steps of charging the ceramic powder and sintering the molded form take place after the step of disposing the winding of the high melting point metal wire on the preform. After sintering, the deformed molded form creates variations in the thickness of a ceramic layer (hereinafter referred to as “the thickness of a dielectric layer”) between the surface of the ceramic heating resistor (that is, the surface on which a wafer is placed) and the plasma-generating electrode.
A non-uniform thickness of the dielectric layer leads to non-uniform generation of plasma, because the intensity of plasma depends on the position at which the plasma-generating electrode is embedded, that is, the thickness of the dielectric layer. Non-uniform generation of plasma leads to non-uniform deposition on a wafer or the like, thus to a reduction in the yield of a product such as a wafer, and thus to deterioration in quality, which is a problem of the above-mentioned method.
Improved yields of products are required due to the trend of higher-density semiconductors and finer wiring rules, and thus a uniform thickness of the dielectric layer is also required. For example, variations in the thickness of the dielectric layer have hitherto been within plus or minus about 0.5 mm from the average thickness thereof. For interlayer dielectrics for use in 1-G DRAMs (dynamic RAMs), variations in the thickness of the dielectric layer, however, must fall within plus or minus 0.05 mm from the average thickness thereof in order that the dielectric layer has a uniform thickness. Thus, a semiconductor manufacturing apparatus has to reduce the range of variations in the thickness of the dielectric layer so as to ensure uniform generation of plasma, as compared to the prior-art apparatuses.
Other and further feature, advantages, and benefits of the present invention will become more apparent from following description taken in conjunction with the following drawings.